*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    display: flex;
    width: 100vw;
    height: 100vh;
    /* display: flex; */
    justify-content: center;
    align-items: center;
}
.container{
    width: 90vw;
    display: flex;
}
.container>div{
    display: flex;
    height: 80vh;
    border-radius: 50px;
    width: 100px;
    position: relative;
    /* flex: 0.5; */
    margin: 10px;
    background-size: cover;
    transition: .5s flex ease-in-out;
}
h3{
    position: absolute;
    bottom: 20px;
    left: 20px;
    /* display: inline-block;
    width: 100px;
    height: 30px; */
    color: #ecf0f1;
    opacity: 0;
    transition: .5s opacity ease-in-out;
}
.show{
    /* flex-grow是这个Demo的关键！！ 因为这个效果才会有这个Demo */
    flex: 1;
}
.show>h3{
    opacity: 1;
}